Measuring audio phase shift through a circuit with a PIC

[HankMcSpank]

Ok, success (of sorts)

By keeping it simple, this code works (many thanks to Paul, whose code sample I used, albeit in McSpank-esque form here)...

PIR2.5 = 0    'Clear the Comp1 interrupt flag
Comp1Time = 0

Main_Loop:
        WHILE PIR2.5 = 0       
        GOTO Main_Loop
        WEND
        TMR1H = 0                    
        TMR1L = 0
        PIR2.5 = 0
        Comp1_count:
        WHILE PIR2.5 = 0
        goto Comp1_count
        wend 
        Comp1Time.Highbyte = TMR1H  
        Comp1Time.Lowbyte = TMR1L
        TMR1H = 0                    
        TMR1L = 0
        PIR2.6 = 0
        'HSEROUT [dec Comp1Time,13, 10]  
        Comp2_count:
        WHILE PIR2.6 = 0
        goto Comp2_count
        wend
        Comp2Time.Highbyte = TMR1H  
        Comp2Time.Lowbyte = TMR1L
        TMR1H = 0                    
        TMR1L = 0
        HSEROUT ["C1=",dec Comp1Time,9,"C2=", dec comp2time, 13, 10]
        PIR2.5 = 0
        goto Main_Loop

ie the C2 count decrements nice & smoothly (& below 336 - yay!) & totally in line with the amount of phase lag....

(green trace is comp1 - non lagged, yellow trace is into comp2 & lagged a miniscule amout)



.....I can get all the way down to 13-14(ish) below which the C2 count gets very jittery (ie successive counts eg 5, 11, 6, 12, 5, - you can see some 19s in that stream above)....but a comp2 count of 13 @1kHz is granular enough for me (accuracy to within 0.936 degrees @1kHz). I'm elated...*BUT*

Quite clearly my original way is causing some issues (p& almost certainly to do with my poor sequence &/or coding), so if this way of doing it works, how can I integrate it into my main program?

My first attempt just now failed...

Here's the screen output...

C1=4909 C2=13
C1=4903 C2=13
C1=4909 C2=13
C1=4909 C2=13
hello
C1=4903 C2=13
C1=4909 C2=13

ie that C1 count has dropped?!! (even though the incoming frequency has remained at 1Khz)

here's what I did (disclaimer: I didn't know how to get the main body of program to 'jump' to to the interrupt handler when Comp1 interrupted, so I deferred back to DT's method as the initial 'trigger')...

Comp1Time       var  word    ' used to amalgamate TMR1 High & Low Bytes.
Comp2Time       var  word

      
INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System  PO90OOO9
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
        INT_Handler   CMP1_INT,  _Comp1_Int,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

T1CON.0= 1  'start timer

Comp1Time = 0 'clear down Comp1Time, prior to starting.
comp2Time = 0  'clear down Comp2Time, prior to starting

@ INT_ENABLE  CMP1_INT     ; enable Comparator 1 interrupts
PIR2.5 = 0    'Clear the Comp1 interrupt flag
Comp1Time = 0
Comp2Time = 0

'Main body of Code****************************************************************

Main:
hserout ["hello", 13, 10]
pause 20
goto Main

END

'**********************Comp1 interrupt handler*********************************************************
Comp1_Int:
Comp1_Loop:
        WHILE PIR2.5 = 0       
        GOTO Comp1_Loop
        WEND
        TMR1H = 0                    
        TMR1L = 0
        PIR2.5 = 0
        Comp1_count:
        WHILE PIR2.5 = 0
        goto Comp1_count
        wend 
        Comp1Time.Highbyte = TMR1H  
        Comp1Time.Lowbyte = TMR1L
        TMR1H = 0                    
        TMR1L = 0
        PIR2.6 = 0
        'HSEROUT [dec Comp1Time,13, 10]  
        Comp2_count:
        WHILE PIR2.6 = 0
        goto Comp2_count
        wend
        Comp2Time.Highbyte = TMR1H  
        Comp2Time.Lowbyte = TMR1L
        TMR1H = 0                    
        TMR1L = 0
        HSEROUT ["C1=",dec Comp1Time,9,"C2=", dec comp2time, 13, 10]
        PIR2.5 = 0
        
@ INT_RETURN